If fuel evaporation from a fuel tank of an automobile and/or a combustible gas mixture preparing device, such as a carburetor, is emitted into the atmosphere, air pollution is caused due to hydrocarbons (HC) contained in the fuel. Devices are known which are provided with a casing accomodating fuel gas absorbing agents therein and which prevent air pollution due to evaporated fuel as well as evaporative fuel loss.
Such a device for preventing evaporative fuel loss is communicated with a fuel tank and/or a carburetor of a vehicle so that fuel, which is evaporated when the temperature of the fuel tank or the carburetor rises, is absorbed in the fuel gas absorbing agents. On the other hand when the engine of the vehicle is started, the fuel, which has been absorbed in the fuel gas absorbing agents, is purged by air introduced through an atmospheric port formed at the bottom of the casing, and it, together with the atmospheric air, is led into combustion chambers of the engine through the intake system of the engine and is burnt there. As a result, emission of hydrocarbons into the atmosphere is prevented and air pollution caused thereby is thus prevented.
It is preferable that a device for preventing evaporative fuel loss, especially for use on an automobile, can absorb a large amount of fuel while the volume thereof is small, because the device can readily be installed on the vehicle. On the other hand, to increase the so called utilizing efficiency of fuel gas absorbing agents in the device for preventing evaporative fuel loss, it is desirable that a large amount of air supplied from an evaporative fuel source and containing evaporated fuel therein be in contact with a large amount of fuel gas absorbing agents, so that the evaporated fuel is effectively absorbed in the fuel gas absorbing agents.
Based on the results obtained from various tests conducted by the inventors of the present invention, the inventors confirmed that the utilizing efficiency could be increased when a casing of a device for preventing evaporative fuel loss was formed in a straight slender shape. However, such a device having a straight slender shape was difficult to install on a vehicle. To easily install the device on a vehicle, the slender shaped casing was serpentined so that the outer shape of the entire device was similar to that of the conventionally known device. However, such a device wherein a slender casing was serpentined did not have such a high utilizing efficiency as a device having a straight slender casing did.
The inventors believe that the phenomenon mentioned above is caused by a fact that, when a serpentined casing is used, air containing evaporated fuel may substantially flow along a path connecting the edges of the serpentined casing, which path is the shortest air flow path. As a result, only a part of fuel gas absorbing agents in the slender casing can be utilized for effectively absorbing fuel.